Image: The Colorful Lives of the Outer Planets

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ABOUT THIS IMAGE:

Atmospheric features on Uranus and Neptune are revealed in
images taken with the Space Telescope Imaging Spectrograph
and the Advanced Camera for Surveys aboard NASA's Hubble
Space Telescope. The observations were taken in August 2003.

The top row reveals Uranus and Neptune in natural colors,
showing the planets as they would appear if we could see them
through a telescope. The images are made of exposures taken
with filters sensitive to red, green, and blue light. In the
bottom images, astronomers used different color filters to
detect features we can't see. The photographs demonstrate
that, by using certain types of color filters, astronomers can
extract more information about a celestial object than our eyes
normally can see.

At first glance, the top row of images makes the planets
appear like twins. But the bottom row reveals that Uranus
and Neptune are two different worlds. Uranus's rotational
axis, for example, is tilted almost 90 degrees to Neptune's
axis. The south poles of Uranus and Neptune are at the left
and bottom, respectively. Both are tilted slightly toward
Earth. Uranus also displays more contrast between both
hemispheres. This may be caused by its extreme seasons.

Both planets display a banding structure of clouds and hazes
aligned parallel to the equator. Additionally, a few discrete
cloud features appear bright orange or red. The color is due
to methane absorption in the red part of the spectrum.
Methane is third in abundance in the atmospheres of Uranus
and Neptune after hydrogen and helium, which are both
transparent. Colors in the bands correspond to variations in
the altitude and thickness of hazes and clouds. The colors
allow scientists to measure the altitudes of clouds
from far away.